<span>The long piece should measure 7.5 feet or 7'6" (7 foot 6 inches).
If x is the length of the short piece then the length of the long piece must be 3x. The total length of the uncut beam is 10 foot.
This can be represented by :
x + 3x = 10
4x = 10
x = 2.5
As x = 2.5 = length of short piece, then the long piece measures 3x = 3(2.5) = 7.5 feet.
There are 12 inches in a foot so 7.5 feet = 7'6"</span>
7/9 because if you simplify 21/27 you have to divide it by something that can go into both equally, which in this case is 3
We have,

Introduce variable
such that 
The sum
is therefore 
So,
(sadia's age)
(father's age)
Hope this helps :)
My first impulse is to say you don't provide enough info with which to solve this problem. We need to know how many inches in the model correspond to 1 foot in the actual plane (that is, the scale factor). What is the scale factor here?